Hi -
Avianca for *A. Just as a crediting vehicle.
AS - MVPG75K. Enough said.
B6 - I fly them enough to get Mosaic. the FF program is nothing special (yet), but between them and AS I have very good N/S coverage along both coasts, very good TCON city pair coverage and very good Midcon coverage to/from each coast.
To the point where I now rarely fly WN and nobody else domestically.
As to FF redemptions, I use B6 for APEX (for those that remember the term) domestic and AS for Intl F/J.